JSFiddle - React, Tailwind, and code Playground

by andrei

CSS

body {
    white-space: pre
}

JavaScript

var MONEY = 35 * 100, // in cents
    firstTotal = 10,
    secondTotal = 16,
    thirdTotal = 26,
    answer = [];

var getAllCombinationsForAFarmer = function(total, priceBeforeLunch, priceAfterLunch) {
    var soldBeforeLunch = 0,
        combinations = {};

    while (soldBeforeLunch <= total) {
        var madeDuringaDay = soldBeforeLunch * priceBeforeLunch + (total - soldBeforeLunch) * priceAfterLunch;

        if (madeDuringaDay == MONEY) {
            combinations[priceBeforeLunch] = priceAfterLunch;
        }
        soldBeforeLunch++;
    }
    return combinations;
};

for (var priceBeforeLunch = 0; priceBeforeLunch <= MONEY; priceBeforeLunch++) {
    for (var priceAfterLunch = 0; priceAfterLunch < priceBeforeLunch; priceAfterLunch++) {
        var firstCombos = getAllCombinationsForAFarmer(firstTotal, priceBeforeLunch, priceAfterLunch),
            secondCombos = getAllCombinationsForAFarmer(secondTotal, priceBeforeLunch, priceAfterLunch),
            thirdCombos = getAllCombinationsForAFarmer(thirdTotal, priceBeforeLunch, priceAfterLunch);

        if (Object.keys(firstCombos).length && Object.keys(secondCombos).length && Object.keys(thirdCombos).length) {

            // now try to find all possible matches from all of combos
            Object.keys(firstCombos).forEach(function (key) {
                var after1 = firstCombos[key],
                    after2 = secondCombos[key],
                    after3 = thirdCombos[key];

                if (after1 == after2 && after2 == after3) {
                    answer.push({
                        before: priceBeforeLunch,
                        after: priceAfterLunch
                    });
                }
            });
        }
    }
}

document.querySelectorAll("body")[0].innerHTML = "FOUND ANSWER: <br/> "+ JSON.stringify(answer, null, 4);